Developments in the use of plasma exchange and adjunctive therapies to treat immune-mediated thrombotic thrombocytopenic purpura

Best practices and recommendations for drug regimens and plasma exchange for immune thrombotic thrombocytopenic purpura

INTRODUCTION

Thrombotic thrombocytopenic purpura (TTP) is a life-threatening thrombotic microangiopathy characterized by microangiopathic hemolytic anemia, thrombocytopenia, and organ injury. TTP pathophysiology is based on a severe ADAMTS13 deficiency, and is a medical emergency with fatal outcome if appropriate treatment is not initiated promptly.

AREAS COVERED

Authors will review the best options currently available to minimize mortality, prevent relapses, and obtain the best clinical response in patients with immune TTP (iTTP). Available bibliography about iTTP treatment has been searched in Library's MEDLINE/PubMed database from January 1990 until April 2021.

EXPERT OPINION

The generalized use of plasma exchange marked a paradigm in the management of iTTP. In recent years, strenuous efforts have been done for a better understanding of the pathophysiology of this disease, improve diagnosis, optimize treatment, reduce mortality, and prevent recurrences. The administration of front-line rituximab and, more recently, the availability of caplacizumab, the first targeted therapy for iTTP, have been steps toward a further reduction in early mortality and for the prevention of relapses.

High Incidence of Thrombotic Thrombocytopenic Purpura Exacerbation Rate Among Patients With Morbid Obesity and Drug Abuse

This study aims to identify the baseline patient characteristics, clinical presentation, and response to treatment of 11 patients who were diagnosed with thrombotic thrombocytopenic purpura (TTP) between 2014 and 2020 at Brookdale University Hospital Medical Center, Brooklyn, NY. Laboratory and clinical parameters were recorded for 29 patients who received plasmapheresis in this time period. Of 29 patients, 11 had confirmed TTP and one was diagnosed with hereditary TTP. Young, black, and female patients made up the majority of our patient population. A high prevalence of obesity and drug abuse were seen among our patients. Five out of 11 were obese and four of them were morbidly obese; six out of 11 patients were positive for the drug screen including cannabinoids (3), opiates (2), benzodiazepines (1), PCP (1), and methadone (1). Four patients with a positive drug screen had acute kidney injury (AKI), and plasmapheresis helped them enhance their kidney function. We observed a high incidence of AKI and high TTP exacerbation rates in patients who were drug abusers and those who were morbidly obese. There is a paucity of data on the relationship of TTP with obesityor drug abuse and this needs further study.

Immunogenic hotspots in the spacer domain of ADAMTS13 in immune-mediated thrombotic thrombocytopenic purpura

BACKGROUND

Immune-mediated thrombotic thrombocytopenic purpura (iTTP) is caused by anti-ADAMTS13 autoantibodies inducing a severe deficiency of ADAMTS13. Epitope mapping studies on samples obtained during acute iTTP episodes have shown that the iTTP immune response is polyclonal, with almost all patients having autoantibodies targeting the spacer domain of ADAMTS13.

OBJECTIVES

To identify the immunogenic hotspots in the spacer domain of ADAMTS13.

PATIENTS/METHODS

A library of 11 full-length ADAMTS13 spacer hybrids was created in which amino acid regions of the spacer domain of ADAMTS13 were exchanged by the corresponding region of the spacer domain of ADAMTS1. Next, the full-length ADAMTS13 spacer hybrids were used in enzyme-linked immunosorbent assay to epitope map anti-spacer autoantibodies in 138 samples from acute and remission iTTP patients.

RESULTS

Sixteen different anti-spacer autoantibody profiles were identified with a similar distribution in acute and remission patients. There was no association between the anti-spacer autoantibody profiles and disease severity. Almost all iTTP samples contained anti-spacer autoantibodies against the following three regions: amino acid residues 588-592, 602-610, and 657-666 (hybrids E, G, and M). Between 31% and 57% of the samples had anti-spacer autoantibodies against amino acid regions 572-579, 629-638, 667-676 (hybrids C, J, and N). In contrast, none of the samples had anti-spacer autoantibodies against amino acid regions 556-563, 564-571, 649-656, and 677-685 (hybrids A, B, L, and O).

CONCLUSION

We identified three hotspot regions (amino acid regions 588-592, 602-610, and 657-666) in the spacer domain of ADAMTS13 that are targeted by anti-spacer autoantibodies found in a large cohort of iTTP patients.

Delayed Thrombotic Complications in a Thrombotic Thrombocytopenic Purpura Patient Treated With Caplacizumab

Thrombotic thrombocytopenic purpura (TTP) is a rare and unpredictable disease with a high mortality rate (90%) if untreated. It results from systemic microvascular thrombosis and leads to profound thrombocytopenia, hemolytic anemia and organ failure of varying severity. However, macrovascular thrombosis has been described in very rare cases. Caplacizumab has emerged as a promising new drug for the management of TTP. We report the case of a patient with idiopathic refractory TTP treated with caplacizumab who developed thrombotic complications upon discontinuation of treatment.

[Clinical characteristics of 83 patients with thrombotic thrombocytopenic purpura]

Objective: To analyze the clinical characteristics, treatment and prognosis of patients with thrombotic thrombocytopenic purpura (TTP) . Methods: 83 patients with TTP from May 1998 to May 2019 were analyzed retrospectively. Results: Among the 83 patients, there were 27 males and 56 females, with a median age of 39 (10-68) years. 41 cases (49.4%) showed pentalogy syndrome and 79 cases (95.2%) showed triad syndrome. 78.0% (46/59) of the patients had a PLASMIC score of 6 or higher. TTP gene mutations was detected in 5 of 10 patients. The activity of von Willebrand factor-cleaving protease (ADAMTS13) , which was detected in 10 patients before plasma exchange (PEX) , was less than 10% in 9 patients. 83 patients were treated with PEX/plasma infusion and glucocorticoid, 35 of which were treated combined with rituximab and/or immunosuppressant. The median follow-up was 34 (1-167) months, the effective rate was 81.9%, the remission rate was 63.9%, the relapse rate was (35.7 ±7.1) %, and the 3-year overall survival (OS) rate was (78.6 ±4.6) %. The effective rate (72.9%vs 94.3%, P=0.019) and OS rate[ (63.8±7.5) %vs (94.3±3.9) %, χ(2)=8.450, P=0.004] in the group treated with PEX/PI and glucocorticoid alone were lower than those in the group treated combined with rituximab and/or immunosuppressant. COX multivariate analysis showed that age (HR=1.111, 95%CI 1.044-1.184, P=0.001) and alanine transaminase (ALT) /aspartate aminotransferase (AST) (HR=1.353, 95%CI 1.072-1.708, P=0.011) were independent risk factors for OS. Conclusion: Most patients with TTP have triad syndrome, accompanied by a decrease in ADAMTS13 activity. Plasma infusion and glucocorticoid combined with rituximab, immunosuppressive therapy could improve overall survival. The prognosis of patients with older age and high ALT/AST ratio is poor.